1. Field of the Invention
The present invention relates generally to boilers or heaters for heating water, and more particularly, but not by way of limitation, to a control system for managing and interfacing a plurality of boilers.
2. Description of the Prior Art
To service facilities having significant demand for heat input into the water supply system, it is well-known in the prior art to employ multiple water heating units, working with coordinated efforts, to satisfy the demand. One such prior art water heating system is based on the KNIGHT™ XL, which has been marketed by Lochinvar Corporation, the assignee of the present invention. The KNIGHT XL features SMART SYSTEM™, which coordinates the operation of a group of individual KNIGHT XL water heating units so that the individual units may function, in concert, to supply heat input into a water supply system.
Specifically, the SMART SYSTEM includes a cascading sequencer. SMART SYSTEM selects one water heating unit as the leader. Provided the heat input demand is less than the capacity of the leader, SMART SYSTEM modulates the operation of the leader to match the heat input demand (water heaters having continuously variable outputs over a range of outputs are well known in the prior art, exemplary systems include those disclosed in U.S. Pat. No. 4,852,524 to Cohen, U.S. Pat. No. 5,881,681 to Stuart, and U.S. Pat. No. 6,694,926 to Baese et al.). If the heat input demand exceeds the capacity of the leader, SMART SYSTEM activates a second water heating unit to handle the excess heat input demand, i.e. the heat input demand above the capacity of the leader “cascades” to the second water heating unit. Keeping the output of the leader at a constant output level, SMART SYSTEM then modulates the operation of the second water heating unit according the excess heat input demand. If the heat input demand exceeds the combined capacity of the leader and the second water heating unit then cascading continues as additional water heating units activate in sequence until enough units are in operation to satisfy the heat input demand. Conversely, when the heat input demand decreases, SMART SYSTEM reverses the cascading process.
Rather than operate the individual water heating units in a cascaded configuration as described above, other prior art water heating control systems employ different schemes. For example, one prior art scheme operates a first water heater in a predetermined range, a range less than the operational limits of the water heater. When the input heat demand causes the first water heater to exceed the predetermined range, a second water heater is activated. The first and second water heaters are then operated in the predetermined range until the heat input demand causes the first and second water heaters to operate outside of the range. When this happens a third water heater is activated and the first, second, and third water heaters operate in the predetermined range. This process continues as additional water heaters are needed to satisfy the input heat demand. The aim of this scheme is to keep the water heaters operating in the predetermined range.
Whether the need to operate a group of individual water heating units as a single system arises from efficiency concerns or the inability of a single water heating unit to meet the heat input demand of a water supply system, the implementation of control systems capable of effectively interfacing and managing the coordinated operation of multiple water heating units is of great import. Without effective management and coordination, the collection of individual water heating units may operate inefficiently or simply fail to satisfy the input heat demands of a water supply system. Further, the absence of adequate interfacing, i.e. communication with and monitoring of the heating system, may result in delays when responding to events that require attention, such as fault conditions or adjusting the system's operating parameters. It is these problems at which the present invention is directed.